German Patent DE-PS 32 11 813 and corresponding U.S. Pat. No. 4,499,603, EILERS, disclose a radio receiver which does not merely wait for the transmission of a warning message and its associated recognition signal on an auxiliary carrier, but rather also monitors for reception of a recognition signal for interrupting traffic announcements and, upon receipt of this recognition signal, resets a timer switch or other timing element to zero. If the timer switch is not reset to zero during a 24-hour period, an error indication is generated.
That apparatus is based upon the assumption that traffic announcements will be broadcast a plurality of times each day. As long as the timer switch is reset to zero by the recognition signals of the traffic announcements, the warning receiver remains ready to receive any warning message, even though it is characterized by some other recognition signal, such as the signals used only in emergencies.
The dead time of the apparatus is 24 hours. This known receiver is not adapted to process other recognition signals. This known receiver has the disadvantage that it is impossible to distinguish whether the receiver is malfunctioning or has merely, by some chance, not received any traffic announcements within the preceeding 24 hours.